Residue removal by supercritical fluids

ABSTRACT

A method for the removal of residue from an etched precision surface such as a semiconductor sample is provided which comprises exposing said precision surface to a supercritical fluid or liquid CO 2  under appropriate conditions that are sufficient to remove the residue from the precision surface. Cryogenic aerosol may be used in conjunction with either the supercritical fluid or liquid CO 2 .

TECHNICAL FIELD

The present invention relates to a method for removing residue materialfrom a precision surface, e.g. a semiconductor sample, which has beenfirst subjected to an etching process, such as reactive ion etching,(RIE). Specifically, the present invention provides a method forremoving residue formed by an etching process on a precision surfacesuch as a semiconductor sample which comprises exposing the precisionsurface to a supercritical fluid under conditions which are sufficientto remove the residue material therefrom. An optional step of using acryogenic aerosol after exposing the precision surface to asupercritical fluid is also contemplated herein. The process of thepresent invention eliminates the use of prior art solvents and acids inselected aspects of advanced semiconductor manufacturing processes forremoving residue from a precision surface, e.g. a semiconductor sample.

In another embodiment of the present invention, liquid CO₂ is used asthe solvent for removing residue from a precision surface, e.g. asemiconductor sample, which has been first subjected to an etchingprocess such as reactive ion etching (RIE). This embodiment comprisesexposing the precision surface containing the etched residue to liquidCO₂ under conditions which are sufficient to remove the residue from theprecision surface. An optional step of using cryogenic aerosol to removeresidue remaining after liquid CO₂ treatment is also contemplatedherein.

BACKGROUND OF THE INVENTION

In the field of advanced semiconductor manufacturing, it is well knownto expose a semiconductor sample, such as a semiconductor wafercontaining blanket metal or insulating films and a photoresist exposedwith patterns to a reactive ion etching (RIE) process using a mixture ofgases containing but not limited to chlorine and/or fluorine. Thepurpose of such an etching process is to define patterns in the films.The photoresist is then typically stripped in an oxygen plasma. Theremaining residues often need to be removed by chemicals and/or solventsin order to achieve high yield.

For example, Al metal etching is the most commonly used to define wiringon the semiconductor wafers. Despite cleaning and rinsing thesemiconductor wafer, unwanted residue still remains on the top and thesidewalls of the metal lines. This unwanted residue, which remains onthe top and sidewalls of the metal lines, reportedly includes theelements carbon, hydrogen, silicon, aluminum, fluorine, chlorine andoxygen. Such residue, which is referred to herein as RIE residue, isknown to be conductive enough to cause shorts between metal lines.Moreover, the RIE residue may also cause adhesion problems between themetal lines and the overlying insulator. The RIE residue on metal linesmay cause corrosion of the semiconductor sample. The RIE residue onpolysilicon lines or oxide vias also cause yield loss problems. Thus,there is considerable interest in the field of advanced semiconductormanufacturing for developing a chemically safe and easy method forremoving the RIE residue from a semiconductor sample.

The current method which is typically being used for removal of thisunwanted RIE residue in advanced semiconductor manufacturing processesinvolves soaking the etched semiconductor sample in an acid bath.

These and other objectives are met by the present method which uses asupercritical fluid or liquid CO₂ as solvents for removing the residuefrom a precision surface which has been first subjected to an etchingprocess.

It is emphasized that supercritical fluids, such as supercritical fluidCO₂, are, however, currently being used in semiconductor processing fordeveloping a resist pattern layer on a substrate. Such a process isdisclosed, for example, in U.S. Pat. No. 4,944,837 to Nishikawa et al.Specifically, Nishikawa et al. provides a method of forming a patternedresist film having a predetermined pattern on a surface layer formed ona substrate comprising the steps of depositing a resist film on thesurface layer, pre-processing the resist film into a pre-processedresist film which is attached to the surface layer and which has alatent image of the predetermined pattern, and processing thepre-processed resist film into the patterned resist film. In accordancewith the disclosure of Nishikawa et al., the processing step comprisesintroducing the pre-processed resist film together with the substrateinto a supercritical atmosphere and developing the pre-processed film ina supercritical atmosphere to selectively remove the pre-processed film.

Other examples of using supercritical fluids in semiconductormanufacturing are disclosed in U.S. Pat. Nos. 5,185,296 and 5,304,515,both to Morita et al. In both of these disclosures, supercritical fluidsare used for forming a dielectric thin film or pattern thereof on thesurface of a semiconductor substrate. As in the above reference toNishikawa et al., the supercritical fluids are used in both of theMorita et al. references to develop the pattern resist film on thesurface of the semiconductor substrate.

In an article by ziger et al. entitled "Compressed Fluid Technology:Application to RIE-Developed Resists", AICHE Journal, Vol. 33, No. 10,October 1978, compressed CO₂ i.e., supercritical fluid CO₂, is utilizedin the area of microlithography to extract nonvolatile siloxanemolecules from a host organic polymer.

Despite the use of supercritical fluids in the prior art there is noknown disclosure of using a supercritical fluid to remove residue from aprecision surface such as a semiconductor sample which contains suchresidue thereon.

SUMMARY OF THE INVENTION

The present invention provides an improved method for the removal ofresidue from a precision surface comprising exposing the precisionsurface containing the residue to a supercritical fluid under conditionswhich are sufficient for removing the residue from the precisionsurface. It is emphasized that the residue on the surface is formed bysubjecting the surface to a material removal process such as chemicaletching, ion etching, or laser ablation, in the process of creating ormodifying a precision surface. The residue formed may be on etchedsurfaces or adjacent non-etched surfaces. The residue is then removedfrom the surface by exposure to a supercritical fluid.

The use of supercritical fluids for removing residue from precisionsurfaces such as semiconductor samples eliminates the prior art use of,but not limited to, a carcinogenic bath containing chromic phosphoricacid. Thus, the present invention provides an efficient and safe meansfor removing etchant residue from a precision surface containing suchresidue.

The term "precision surface" as used herein denotes a material which hascontrolled features below the plane of the surface such as cavities,trenches or channels incorporated into the material and or raisedfeatures such as mesas. Cleaning of this type of surface must beselective to the residue and not modify the surface geometry(dimensions). Precision surfaces include, but are not limited to,semiconductors samples, metals, polymers and insulators.

The term "supercritical fluid" is used herein to denote a material whichis under conditions of not lower than a critical temperature, T_(c), andnot less than a critical pressure, P_(c), in a pressure-temperaturediagram of an intended compound. For a complete description on thetheory of supercritical fluids see Kirk-Othmer Encyclopedia of ChemicalTechnology, 3d, Supplement Volume, pp. 872-893. The preferredsupercritical fluid employed in the present invention is CO₂ which maybe used alone or in an admixture with another additive such as Ar, NH₃,N₂, CH₄, C₂ H₄, CHF₃, C₂ H₆, n-C₃ H₈, H₂ O, N₂ O and the like.Surfactants containing at least one CF_(x) functional group may also beused in conjunction with a supercritical fluid.

In another embodiment of the present invention, a two step process forremoving residue from an etched precision surface is provided. Inaccordance with this embodiment of the present invention, an etchedprecision surface containing residue is first exposed to a supercriticalfluid under conditions sufficient to detach said residue from theprecision surface and then the exposed precision surface is contactedwith a cryogenic aerosol to remove the remaining residue not removed bysupercritical fluid treatment from the precision surface.

In a third embodiment of the present invention, liquid CO₂ is used forremoving residue from an etched precision surface containing the same.In accordance with this embodiment of the present invention, an etchedprecision surface containing residue is exposed to liquid CO₂ underconditions sufficient to remove said residue from the precision surface.

In a fourth embodiment of the present invention, liquid CO₂ is used inconjunction with a cryogenic aerosol, in a two step process, to removeresidue from an etched precision surface. In this embodiment of thepresent invention, the etched precision surface containing the residueis exposed to liquid CO₂ under appropriate conditions and then theexposed precision surface is contacted with a cryogenic aerosol underconditions sufficient to remove the remaining residue not previouslyremoved by the liquid CO₂ treatment step from the precision surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the apparatus which is employed in theinstant invention for the removal of residue from a precision surfacesuch as a semiconductor sample.

FIG. 2 is an SEM illustrating the metal line structures of a 200 mmsemiconductor wafer which contains RIE reside, which was broken intoseveral samples for testing.

FIG. 3 is an SEM of a first piece of the wafer of FIG. 2 after exposureto supercritical fluid CO₂ for 2 hrs. at 40° C. and 5840 psi, 50Kmagnification, resolution 600 nm.

FIG. 4 is an SEM of a second piece of the wafer of FIG. 2 after exposureto supercritical CO₂ for 2 hrs. at 80° C. and 5840 psi, 50Kmagnification, resolution 600 nm.

FIG. 5 is an SEM of a third piece of the wafer of FIG. 2 after exposureto supercritical fluid CO₂ for 30 minutes at 40° C. and 5840 psi, 35Kmagnification, resolution 857 nm.

FIG. 6 is an SEM of a fourth piece of the wafer of FIG. 2 after exposureto supercritical fluid CO₂ for 1 hr. at 40° C. and 5840 psi, 60Kmagnification, resolution 500 nm.

FIG. 7 is an SEM of a fifth piece of the wafer of FIG. 2 after exposureto supercritical CO₂ for 2 hr. at 40° C. and 5840 psi, 60Kmagnification, resolution 500 nm.

FIG. 8 is an SEM of a first piece of a 200 mm semiconductor wafer withvias etched in the oxide film shown from the side, 5 KV, 60Kmagnification, resolution 600 nm.

FIG. 9 is an SEM of a second piece of the 200 mm semiconductor wafer ofFIG. 8 with vias etched in the oxide film, shown from the side, afterprocessing in supercritical fluids, 10 KV, 60K magnification, resolution500 nm.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with the first embodiment of the present invention,residue which is present on an etched precision surface is removed fromthe precision surface by using supercritical fluids. Specifically, theresidue is removed from an etched precision surface by exposing theprecision surface to a supercritical fluid under conditions which aresufficient to remove said residue.

It is emphasized that the precision surface is first etched prior toexposing it to a supercritical fluid. Etching of the precision surfacemay be conducted using techniques well known to those skilled in theart. Suitable techniques for etching the precision surface include, butare not limited to, reactive ion etching (RIE), ion beam etching (IBE),plasma etching, laser ablation and the like. Of these etchingtechniques, RIE is particularly preferred in the present invention.Typically, in the prior art, RIE is carried out using gases containing,but not limited to, Cl or F.

The residue left behind after etching a precision surface may containone or more of the following elements: carbon, hydrogen, silicon,aluminum, Ti, Ta, W, Pt, Pd, Ir, Cr, fluorine, chlorine or oxygen.

As stated above, the term "precision surface" is used herein denote amaterial which contains a surface that has cavities, trenches and/orchannels incorporated therein. Suitable precision surfaces that may beemployed in the present invention include, but are not limited to,semiconductor samples, metals such as Al, Si, W, Ti, Ta, Pt, Pd, Ir, Cr,Cu, and Ag, polymers such as polyimides, polyamides and the like, andinsulators. Of these precision surfaces, semiconductor samples areparticularly preferred in the present invention.

It should be noted that the description provided hereinbelow while beingspecific to RIE semiconductor samples is also valid for other types ofprecision surfaces which may be etched by any of the aforementionedetching techniques. For example, the description provided hereinbelowalso applies to an IBE insulator, a laser ablated polymer and the like.

FIG. 1 is a schematic diagram of an apparatus 10 that can be used in thepresent invention for removing RIE residue from a semiconductor samplecontaining the same. Apparatus 10 includes process chamber 12 having asample zone 14 wherein the semiconductor sample 16 is placed. Theprocess chamber 12 is surrounded by heater jacket 18 and contains,optionally, a stirring mechanism 20. Additionally, the process chambercontains inlet line 22, outduct 24 and thermocouple 26. The inlet line22 contains a high pressure pump system 28 which is connected to gascylinder 30 for supplying a supercritical fluid or mixture thereof toprocess chamber 12. Thermocouple 26 is also connected to heater control32 which is utilized for controlling and monitoring the temperature ofthe RIE residue removal process. Apparatus 10 may also include reservoir34 for collecting and/or purifying supercritical fluids that exitprocess chamber 12 through outduct 24. This material may then berecycled into the process chamber via duct 35. Gas cylinder 30 containsa pressurized liquid. The term supercritical fluid refers to the stateof matter of a material above its critical point, i.e., a criticaltemperature, T_(c), and critical pressure, P_(c), at which two phases ofa substance, in equilibrium with each other, become identical, formingone phase. Any supercritical fluid known to those skilled in the artsuch as CO₂ and/or Ar may be used in the present invention provided thatthey are capable of removing the RIE residue from the semiconductorsample. The preferred supercritical fluid is CO₂ which may be used aloneor in an admixture with one or more additives selective from the groupconsisting of Ar, N₂ O, NH₃, N₂, CH₄, C₂ H₄, CHF₃, C₂ H₆, H₂ O, n-C₃ H₈,and the like.

Any grade of supercritical fluid can be employed in the presentinvention. If a low grade of supercritical fluid is employed whichcontains a lot of impurities therein, the supercritical fluid can befirst purified to remove the impurities using techniques well known tothose skilled in the art. For instance, the low grade supercriticalfluid could be purified by passing it through a column prior to enteringthe processing chamber.

It is also emphasized that the supercritical fluid could be combinedwith additives or surfactants which would aid in removing the RIEresidue from the semiconductor sample. Suitable additives include, butare not limited to, those mentioned hereinabove. Of these additives, H₂O is most particularly preferred.

The types of surfactants that may be used in the present inventioninclude any surfactant which contains at least one CF_(x) functionalgroup in its structure.

As shown in FIG. 1, the supercritical fluid is pre-pressurized with ahigh pressure pump. Typically, in the present invention, thesupercritical fluid is pre-pressurized to a pressure of about 1000 psito 6000 psi. More preferably, the supercritical fluid is pre-pressurizedto a pressure of about 3000 psi before entering the processing chamber.The pre-pressurized supercritical fluid is then transferred to theprocessing chamber which contains a semiconductor sample through inletline 22.

The semiconductor samples that can be employed in the present inventionare any semiconductor samples that are processed by RIE or any of theother etching techniques mentioned hereinabove. Illustrated examples ofsuitable semiconductor samples that may be used in the present inventioninclude, but are not limited to, semiconductor wafers, semiconductorchips, ceramic substrates, patterned film structures and the like.

Besides what is used in illustrating the invention, the semiconductorsample, which may be subjected to the method of the present invention,may include one or more of the following materials: titanium silicides,tantalum nitride, tantalum silicide, silicon, polysilicon, siliconnitride, SiO₂, diamond-like carbon, polyimides, polyamides, aluminum,aluminum with copper, copper, tungsten, titanium, palladium, platinum,iridium, chromium, ferroelectric materials and high dielectric materialssuch as BaSrTi or PbLaTi oxides.

The semiconductor sample containing the RIE residue is placed in samplezone 16 of process chamber 12 wherein the sample is exposed to thesupercritical fluid under conditions which are sufficient to remove theRIE residue from the sample while maintaining the supercritical fluidabove its critical temperature and pressure.

Typically, in the present invention the pressure within the processchamber during RIE residue removal is from about 1000 psi to about 6000psi. More preferably, the pressure within the process chamber during RIEresidue removal is about 3000 psi.

The temperature within the processing chamber during the RIE residueremoval which is monitored by thermocouple 26 and controlled bycontroller 32 is generally from about 40° C. to about 80° C. Morepreferably, the temperature within the process chamber during RIEresidue removal is about 40° C.

To ensure effective removal of the RIE residue from the semiconductorsample, the semiconductor sample should be exposed to the supercriticalfluid under the above conditions for about 30 minutes to about 2 hrs.More preferably, the time period for exposure of the semiconductorsample to the supercritical fluid under the above-identified conditionsis about 1 hr.

The supercritical fluid exiting the process chamber through outduct 24may be cleaned, as described above, and recycled back into the apparatusso as to form a closed reactor system. Such a closed reactor system,which is not shown in FIG. 1, would greatly reduce the processing costin producing clean semiconductor samples.

When stirring is employed within the processing chamber, the speed ofthe stirring unit may vary from about 500 rpm. to about 2500 rpm.,preferably about 1000 rpm.

In accordance with the second embodiment of the present invention, amethod for removing residue from an etched precision surface such as aRIE semiconductor sample is provided which comprises the steps ofexposing the precision surface to a supercritical fluid and thencontacting the exposed precision surface to a cryogenic aerosol. Ahighly preferred precision surface used in this embodiment of thepresent invention is a RIE semiconductor sample.

The term "cryogenic aerosol" as used herein denotes a solid jet spraywhich is formed when a relatively high pressure gas liquid mixture isallowed to rapidly expand into a region of lower pressure at cryogenictemperatures, cooling the jet and causing the mixture to solidify.Cryogenic aerosols comprising argon, nitrogen and/or CO₂ may be employedin the present invention in removing residue from a precision surface.

When cryogenic aerosol is used, the cryogenic aerosol contacts theexposed semiconductor sample under conditions which are sufficient toremove the remaining residue detached during the supercritical fluidtreatment process. Such conditions are well known to those skilled inthe art.

In the third embodiment of the present invention, liquid CO₂ is used asthe solvent instead of a supercritical fluid for removing residue from aprecision surface that has been previously etched by one of theaforementioned etching processes. The preferred precision surfaceemployed in this third embodiment of the instant invention is asemiconductor sample which was been etched by RIE.

The apparatus used in this third embodiment of the present invention issimilar to the one shown in FIG. 1 except that the gas cylinder containsgaseous CO₂ which is made into a liquid by pre-pressurizing the gas to atotal pressure of about 880 psi to about 1000 psi. More preferably, thegaseous CO₂ is pressurized to about 880 psi.

Any grade of gaseous CO₂ made be used, however, if the impurity levelwithin the gas is too high the gas should be purified by the aboveidentified techniques prior to be converted into the liquid state.

The conditions used in this third embodiment are not as severe as thatdescribed above since no supercritical fluid is employed. Typically, inthis third embodiment, the pressure within the processing chamber duringresidue removal is from about 880 psi to about 1000 psi. Morepreferably, when liquid CO₂ is employed the pressure within theprocessing chamber is about 880 psi.

The temperature which is used in this third embodiment of the presentinvention is generally from about 25° C. to about 40° C. Morepreferably, when liquid CO₂ is employed, the temperature within theprocessing chamber during residue removal is about 40° C.

Sufficient residue removal using liquid CO₂ is obtained generally withina period of time of from about 30 minutes to about 2 hrs. Morepreferably, sufficient residue removal using liquid CO₂ is generallyobtained within a time period of about 1 hr.

The liquid CO₂ may be used alone or it may be used with one of thesurfactants or additives described hereinabove. The preferred additiveused with liquid CO₂ is H₂ O.

When stirring is employed in this third embodiment, the stirring speedis from about 500 rpm to about 2500 rpm. More preferably, the stirringspeed in the third embodiment is about 1000 rpm.

In the fourth embodiment of the present invention, the residue isremoved from an etched precision surface using a two step process whichcomprises first exposing a precision surface containing etchant residueto liquid CO₂ under conditions defined above and then contacting theexposed semiconductor sample with a cryogenic aerosol under conditionsto remove the remaining residue detached during the liquid CO₂treatment.

The cryogenic aerosol used in this embodiment of the present inventionis the same as that described hereinabove in the second embodiment.Moreover, the conditions are also the same as that reported hereinabove.

The following examples are given to illustrate the scope of the presentinvention. Because these examples are given for illustrative purposesonly, the invention embodied therein should not be limited thereto.

EXAMPLE 1

In this example, RIE residue is removed from semiconductor wafers usingsupercritical fluid CO₂ as the solvent. Specifically, the semiconductorwafers containing a blanket metallization and a patterned photoresistwere first exposed to a typical reactive ion etch process.

After etching of aluminum lines, the photoresist was stripped in an O₂-containing plasma using techniques well known to those skilled in theart.

A Scanning Electron Micrograph (SEM), of one of the wafers afterprocessing is shown in FIG. 2. All the SEM's shown in FIGS. 2-7 of thisexample were done at 10 KEV using various magnifications andresolutions. Views from the top as well as the sides are also shown.Specifically, FIG. 2 shows the metal line structure of the RIE waferwhich contains RIE residue deposit thereon.

Next, pieces of wafers, as shown in FIG. 2, containing RIE residue wereloaded into a high pressure chamber as shown in FIG. 1. Supercriticalextraction grade CO₂ was pre-pressurized to about 5840 psi using amechanical pump and was introduced into the pressure chamber by usingstatic pressure and flow mode. No stirring was utilized in this example.

In a first experiment, one of the wafer pieces was exposed tosupercritical fluid CO₂ for 2 hrs at a temperature of 40° C. and apressure of 5840 psi. An SEM for this experiment is shown in FIG. 3.Specifically, this SEM shows a cleaned semiconductor sample. The sampleinitially contained RIE residue prior to exposure to a supercriticalfluid under the above conditions.

In another experiment, a wafer was exposed to supercritical fluid CO₂for 2 hrs. at a temperature of 80° C. and a pressure of 5840 psi. An SEMfor this experiment is shown in FIG. 4. Again, this SEM illustrates thateffective RIE residue removal is obtained by using the method of thepresent invention.

Further experiments were made at 40° C. and 5840 psi using processingtimes of 30 minutes, 1 hour and 2 hours. Those results are shown inFIGS. 5, 6 and 7, respectively. The RIE residue removal from thesemiconductor wafers was shown to be more effective at 1 or 2 hours thanat 30 minutes.

EXAMPLE 2

In this example, a section of a 200 mm wafer with vias etched in theoxide was subjected to supercritical CO₂.

Residue that was formed in the vias can be seen in FIG. 8 (side view).The wafer was exposed to supercritical fluid CO₂ for 1 hour at 3000 psiand 40° C. with stirring at 500 rpm. As shown in Figure FIG. 9 (sideview), all RIE residue has been removed from the sample under theseconditions.

While this invention has been particularly shown and described withrespect to preferred embodiments thereof, it will be understood by thoseskilled in the art that the foregoing and other changes in form anddetails may be made therein without departing from the spirit and scopeof the invention.

Having thus described our invention, what we claim as new, and desire tosecure by Letter Patent is:
 1. A method for forming a clean precisionsurface comprising providing a reactive ion etched (RIE) precisionsurface having cavities, trenches or channels incorporated therein,wherein said RIE precision surface contains halogenated etched residuethereon; and continuously exposing said RIE precision surface containingsaid halogenated etched residue to a supercritical fluid underconditions sufficient to remove said halogenated etched residue fromsaid RIE precision surface while maintaining the supercritical fluidabove a single critical temperature and pressure.
 2. The method of claim1 wherein the precision surface is a semiconductor sample, a metal, apolymer or an insulator.
 3. The method of claim 2 wherein the precisionsurface is a semiconductor sample.
 4. The method of claim 3 wherein saidsemiconductor sample is a semiconductor wafer, semiconductor chip,ceramic substrate, or other patterned film structure.
 5. The method ofclaim 4 wherein said semiconductor sample is a semiconductor wafer. 6.The method of claim 5 wherein said precision surface contains a materialselected from the group consisting of titanium silicide, tantalumnitride, silicon, polysilicon, silicon nitride, SiO₂, diamond-likecarbon, polyimides, polyamides, aluminum, aluminum with copper, copper,W, Ti, Ta, Pt, Pd, Ir, Cr, ferroelectric materials and high dielectricmaterials.
 7. The method of claim 1 wherein said supercritical fluidcomprises Ar, CO₂ or mixtures thereof.
 8. The method of claim 7 whereinsaid supercritical fluid is CO₂.
 9. The method of claim 1 wherein saidsurface is exposed to said supercritical fluid at a pressure of fromabout 1000 psi to about 6000 psi.
 10. The method of claim 9 wherein saidpressure is about 3000 psi.
 11. The method of claim 1 wherein saidsurface is exposed to said supercritical fluid at a temperature of about40° C. to about 80° C.
 12. The method of claim 1 wherein said surface isexposed to said supercritical fluid for a time period of about 30minutes to about 2 hrs.
 13. The method of claim 12 wherein said time forsaid exposure is about 1 hr.
 14. The method of claim 1 wherein saidsupercritical fluid is purified prior to use thereof.
 15. The method ofclaim 1 wherein said supercritical fluid is stirred at about 500 rpm toabout 2500 rpm.
 16. The method of claim 15 wherein said supercriticalfluid is stirred at about 1000 rpm.
 17. The method of claim 1 wherein anadditive or a surfactant is used with said supercritical fluid.
 18. Themethod of claim 17 wherein said additive is selected from the groupconsisting of Ar, N₂ O, NH₃, N₂, CH₄, C₂ H₄, CHF₃, C₂ H₆, n-C₃ H₈ and H₂O.
 19. The method of claim 18 wherein said additive is H₂ O.
 20. Themethod of claim 17 wherein said surfactant is a surfactant whichcontains at least one CF_(x) functional group.
 21. The method of claim 1wherein said residue contains at least one element selected from thegroup consisting of carbon, hydrogen, silicon, aluminum, Ti, Ta, W, Pt,Pd, Ir, Cr, fluorine, chlorine and oxygen.
 22. The method of claim 1further comprising contacting said supercritical fluid exposed precisionsurface with a cryogenic aerosol under conditions sufficient to removeany remaining residue from said exposed precision surface.
 23. Themethod of claim 22 wherein said cryogenic aerosol is comprised of Ar,N₂, CO₂ or a mixture thereof.